Most quasidiagonal operators are not block-diagonal

Herrero, Domingo A.

doi:10.1090/S0002-9939-1988-0964866-3

Most quasidiagonal operators are not block-diagonal
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Proc. Amer. Math. Soc. 104 (1988), 845-851 Request permission

Abstract:

The set of all block-diagonal operators is a dense first category subset of the class $(QD)$ of all quasidiagonal operators. On the other hand, the subset of all irreducible quasidiagonal operators with thin spectra, that are similar to block-diagonal ones, includes a ${G_\delta }$-dense subset of $(QD)$.

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